How great was the Great American Eclipse? The featured HDR image shows it to be perhaps greater than we knew. On August 21 of last year, the Moon blocked the Sun for a few minutes along a narrow path across the USA. Although one of the most photographed events in human history, this image -- only recently completed after an extraordinary amount of digital processing -- shows one of the most detailed depictions of a solar corona ever taken. Composed of extremely hot gas, the solar corona is only visible to the unaided eye during a total solar eclipse. The featured image combined over 70 images of different time exposures. The series of complementary HDR images recovered enough detail to see motion of the solar corona. The images were taken in Unity, Oregon in the morning to get steady atmospheric seeing conditions. The next total solar eclipse visible on Earth will be in 2019 July, while the next one visible across North America and the USA will occur in 2024 April. via NASA

Flanked by satellite galaxies of the Milky Way a volcanic peak rises from this rugged horizon. The southern night skyscape looks toward the south over Laguna Lejia and the altiplano of the Antofagasta Region of northern Chile. Extending the view across extragalactic space, the Large (right) and Small Magellanic Clouds are so named for the 16th century Portuguese explorer Ferdinand Magellan, leader of planet Earth's first circumnavigation. The larger cloud lies some 180,000 light-years, and the smaller 210,000 light-years beyond the mountaintop. Left of the Small Cloud of Magellan and also reflected in the foreground watery shallows on that starry night, 47 Tucanae shines like a bright star. A globular star cluster that roams the halo of the Milky Way, 47 Tucanae is about 13,000 light-years away. via NASA

Friday, April 27, 2018

This grand allsky view of our Milky Way and nearby galaxies is not a photograph. It's a map based on individual measurements for nearly 1.7 billion stars. The astronomically rich data set used to create it, the sky-scanning Gaia satellite's second data release, includes remarkably precise determinations of position, brightness, colour, and parallax distance for 1.3 billion stars. Of course, that's about 1 percent of the total number of stars in the Milky Way. Still, the flat plane of our galaxy dominates the view. Home to most Milky Way stars it stretches across the center of Gaia's stellar data map. Voids and rifts along the galactic plane correspond to starlight-obscuring interstellar dust clouds. At lower right are stars of the Large and Small Magellanic Clouds, neighboring galaxies that lie just beyond the Milky Way. via NASA

You couldn't really be caught in this blizzard while standing by a cliff on Churyumov-Gerasimenko, also known as comet 67P. Orbiting the comet in June of 2016 the Rosetta spacecraft's narrow angle camera did record streaks of dust and ice particles though, as they drifted across the field of view near the camera and above the comet's surface. Still, some of the bright specks in the scene are likely due to a rain of energetic charged particles or cosmic rays hitting the camera, and the dense background of stars in the direction of the constellation Canis Major. Click on this single frame to play and the background stars are easy to spot as they trail from top to bottom in an animated gif (7.7MB). The 33 frames of the time compressed animation span about 25 minutes of real time. The stunning gif was constructed from consecutive images taken while Rosetta cruised some 13 kilometers from the comet's nucleus. via NASA

The Blue Horsehead Nebula looks quite different in infrared light. In visible light, the reflecting dust of the nebula appears blue and shaped like a horse's head. In infrared light, however, a complex labyrinth of filaments, caverns, and cocoons of glowing dust and gas emerges, making it hard to even identify the equine icon. The featured image of the nebula was created in three infrared colors (R=22, G=12, B=4.6 microns) from data taken by NASA's orbiting Wide Field Infrared Survey Explorer (WISE) spacecraft. The nebula is cataloged as IC 4592 and spans about 40 light years, lying about 400 light years away toward the constellation Scorpius along the plane of our Milky Way Galaxy. IC 4592 is fainter but covers an angularly greater region than the better known Horsehead Nebula of Orion. The star that predominantly illuminates and heats the dust is Nu Scorpii, visible as the yellow star left of center. via NASA

Did you see it? One of the more common questions during a meteor shower occurs because the time it takes for a meteor to flash is typically less than the time it takes for a head to turn. Possibly, though, the glory of seeing bright meteors shoot across and knowing that they were once small granules on another world might make it all worthwhile, even if your observing partner(s) could not share in every particular experience. Peaking late tonight, a dark sky should enable the Lyrids meteor shower to exhibit as many as 20 visible meteors per hour from some locations. In the featured composite of nine exposures taken during the 2012 shower, a bright Lyrid meteor streaks above picturesque Crater Lake in Oregon, USA. Snow covers the foreground, while the majestic central band of our home galaxy arches well behind the serene lake. Other meteor showers this year -- and every year -- include the Perseids in mid-August and the Leonids in mid-November. via NASA

Friday, April 20, 2018

Wikipedia picture of the day on April 21, 2018: A port security boat assigned to Martime Expeditionary Squadron (MSRON) 1 patrols the waters near Kuwait Naval Base. MSRON-1 is deployed supporting maritime security operations and port security operations in the U.S. 5th Fleet area of responsibility. Wikipedia"

Have you seen the Moon lately? On April 18, its waxing sunlit crescent moved through planet Earth's night across a background of stars in the Hyades. Anchored by bright star Aldebaran, the nearby, V-shaped star cluster and complete lunar orb appear in this telephoto image. The engaging skyview is actually digitally composed from a series of varying exposures. Recorded in 1/60th of a second, the shortest in the series captures the Moon's bright crescent in sharp detail. Longer exposures, ranging up to 15 seconds, capture fainter background stars as well as earthshine, visible to the eye as the earthlit lunar night side. via NASA

Except for the rings of Saturn, the Ring Nebula (M57) is probably the most famous celestial band. Its classic appearance is understood to be due to our own perspective, though. The recent mapping of the expanding nebula's 3-D structure, based in part on this clear Hubble image,indicates that the nebula is a relatively dense, donut-like ring wrapped around the middle of a (American) football-shaped cloud of glowing gas. The view from planet Earth looks down the long axis of the football, face-on to the ring. Of course, in this well-studied example of a planetary nebula, the glowing material does not come from planets. Instead, the gaseous shroud represents outer layers expelled from the dying, once sun-like star, now a tiny pinprick of light seen at the nebula's center. Intense ultraviolet light from the hot central star ionizes atoms in the gas. The Ring Nebula is about one light-year across and 2,000 light-years away. via NASA

Monday, April 16, 2018

Wikipedia picture of the day on April 17, 2018: View of the Castle of Zafra, Campillo de Dueñas, Guadalajara, Spain. The castle was built in the late 12th or early 13th centuries on a sandstone outcrop and stands on the site of a former Visigothic and Moorish fortification that fell into Christian hands in 1129. It had considerable strategic importance as a virtually impregnable defensive work on the border between Christian and Muslim-ruled territory. The castle was never conquered and was successfully defended against the King of Castile in the 13th century. The successful completion of the Reconquista at the end of the 15th century ended its military significance. Wikipedia"

What would it look like to fly over the North Pole of Jupiter? A fictional animation made from real images and data captured by NASA's Juno spacecraft shows an answer. Since the pole is presently in shadow, the video uses infrared light emitted by Jupiter -- specifically an infrared color where the hottest features glows the brightest. As the animation starts, Juno zooms in on the enormous world. Soon, one of the eight cyclones orbiting the North Pole is featured. One by one, all eight cyclones circling the pole are inspected, each the size of an entire continent on Earth, and each containing bumpy and fragmented spiral walls. The virtual trip ends with a zoom out. Studying Jovian cyclones helps humanity to better understand dangerous storm systems that occur here on Earth. Juno has recently concluded another close pass by Jupiter -- Perijove 12 -- and seems healthy enough to complete several more of the two-month orbits. via NASA

Sunday, April 15, 2018

Wikipedia picture of the day on April 16, 2018: A MK-46 exercise torpedo is launched from the deck of Arleigh Burke-class guided-missile destroyer USS Mustin (DDG 89) during a torpedo launch exercise in Philippine Sea. Wikipedia"

What's that rising from the clouds? The space shuttle. Sometimes, if you look out the window of an airplane at just the right time and place, you see something unusual -- in this case a space shuttle launching to orbit. The featured image of Endeavour's final launch in 2011 May was captured from a NASA shuttle training aircraft. Taken well above the clouds, the image can be matched with similar images of the same shuttle plume taken below the clouds. Hot glowing gasses expelled by the engines are visible near the rising shuttle, as well as a long smoke plume. A shadow of the plume appears on the cloud deck, indicating the direction of the Sun. The US Space Shuttle program concluded in 2011, and Endeavour can now be visited at the California Science Center. Planned for tomorrow, however, is a different launch -- that of the Transiting Exoplanet Survey Satellite (TESS) aboard a SpaceX Falcon 9 rocket. via NASA

Deep shadows create dramatic contrasts between light and dark in this high-resolution close-up of the martian surface. Recorded on January 24, 2014 by the HiRISE camera onboard the Mars Reconnaissance Orbiter, the scene spans about 1.5 kilometers. From 250 kilometers above the Red Planet the camera is looking down at a sand dune field in a southern highlands crater. Captured when the Sun was about 5 degrees above the local horizon, only the dune crests were caught in full sunlight. A long, cold winter is coming to the southern hemisphere and bright ridges of seasonal frost line the martian dunes. via NASA

Friday, April 13, 2018

Wikipedia picture of the day on April 14, 2018: Indosylvirana urbis, Urban Golden-backed Frog, is a species of frog known only in the southern Western Ghats in Kerala. Here it is resting comfortably in the pink colored boat-shaped bract of the Curcuma angustifolia (East Indian Arrowroot) flower. Wikipedia"

Wednesday, April 11, 2018

Wikipedia picture of the day on April 12, 2018: The Soyuz TMA-13 spacecraft, carrying Expedition 18 Commander Michael Fincke, Flight Engineer Yury V. Lonchakov and American spaceflight participant Richard Garriott, launched Sunday, October 12, 2008, from the Baikonur Cosmodrome in Kazakhstan. The three crew members docked with the International Space Station on October 14. Garriott returned to Earth on October 24 with two members of the Expedition 17 crew, while Fincke and Lonchakov remained on the station for six months. Wikipedia"

Was this flash the farthest star yet seen? An unexpected flash of light noticed fortuitously on Hubble Space Telescope images may prove to be not only an unusual gravitational lensing event but also an image of a normal star 100 times farther away than any star previously imaged individually. The featured image shows the galaxy cluster on the left complete with many yellowish galaxies, while on the right is an expanded square where a source appeared in 2016 that was not evident in 2011. The spectrum and variability of this source are strangely unlike a supernova, but rather appear more consistent with a normal blue supergiant star magnified by about a factor of 2000 by a confluence of aligned gravitational lenses. Dubbed Icarus, the source is in a galaxy well behind the galaxy cluster and far across the universe -- at redshift 1.5. If the lens interpretation is correct and Icarus is not an exploding star, further observations of it and other similarly magnified stars could give information about the stellar and dark matter content in the galaxy cluster and the universe. via NASA

Tuesday, April 10, 2018

Wikipedia picture of the day on April 11, 2018: Overview of the courtyard of the Agha Bozorg mosque, a historical mosque in Kashan, Iran. The mosque, located in the center of the city, was built in the late 18th century by master-mimar Ustad Haj Sa'ban-ali. The mosque has of two large iwans, one in front of the mihrab and the other by the entrance and the courtyard in the middle. Wikipedia"

What's that in the sky? An aurora. A large coronal hole opened last month, a few days before this image was taken, throwing a cloud of fast moving electrons, protons, and ions toward the Earth. Some of this cloud impacted our Earth's magnetosphere and resulted in spectacular auroras being seen at high northern latitudes. Featured here is a particularly photogenic auroral curtain captured above Tromsø Norway. To the astrophotographer, this shimmering green glow of recombining atmospheric oxygen appeared as a large dragon, but feel free to share what it looks like to you. Although now past Solar Maximum, our Sun continues to show occasional activity creating impressive auroras on Earth visible even last week. via NASA

One of the most spectacular solar sights is an explosive flare. In 2011 June, the Sun unleashed somewhat impressive, medium-sized solar flare as rotation carried active regions of sunpots toward the solar limb. That flare, though, was followed by an astounding gush of magnetized plasma -- a monster filament seen erupting at the Sun's edge in this extreme ultraviolet image from NASA's Solar Dynamics Observatory. Featured here is a time-lapse video of that hours-long event showing darker, cooler plasma raining down across a broad area of the Sun's surface, arcing along otherwise invisible magnetic field lines. An associated coronal mass ejection, a massive cloud of high energy particles, was blasted in the general direction of the Earth,and made a glancing blow to Earth's magnetosphere. via NASA

Ten thousand years ago, before the dawn of recorded human history, a new light would have suddenly have appeared in the night sky and faded after a few weeks. Today we know this light was from a supernova, or exploding star, and record the expanding debris cloud as the Veil Nebula, a supernova remnant. This sharp telescopic view is centered on a western segment of the Veil Nebula cataloged as NGC 6960 but less formally known as the Witch's Broom Nebula. Blasted out in the cataclysmic explosion, the interstellar shock wave plows through space sweeping up and exciting interstellar material. Imaged with narrow band filters, the glowing filaments are like long ripples in a sheet seen almost edge on, remarkably well separated into atomic hydrogen (red) and oxygen (blue-green) gas. The complete supernova remnant lies about 1400 light-years away towards the constellation Cygnus. This Witch's Broom actually spans about 35 light-years. The bright star in the frame is 52 Cygni, visible with the unaided eye from a dark location but unrelated to the ancient supernova remnant. via NASA

Thursday, April 5, 2018

Wikipedia picture of the day on April 6, 2018: These well-preserved basalt columns are known as "Symphony of the Stones" and are located in the Garni Gorge, near Yerevan, capital city of Armenia. The columns are visible because they were carved out by the Goght River. Wikipedia"

About 70 million light-years distant, gorgeous spiral galaxy NGC 289 is larger than our own Milky Way. Seen nearly face-on, its bright core and colorful central disk give way to remarkably faint, bluish spiral arms. The extensive arms sweep well over 100 thousand light-years from the galaxy's center. At the lower right in this sharp, telescopic galaxy portrait the main spiral arm seems to encounter a small, fuzzy elliptical companion galaxy interacting with enormous NGC 289. Of course the spiky stars are in the foreground of the scene. They lie within the Milky Way toward the southern constellation Sculptor. via NASA

The robotic rover Opportunity sometimes passes small craters on Mars. Pictured here in 2010 is Intrepid Crater, a 20-meter across impact basin slightly larger than Nereus Crater that Opportunity had chanced across previously. The featured image is in approximately true color but horizontally compressed to accommodate a wide angle panorama. Intrepid Crater was named after the lunar module Intrepid that carried Apollo 12 astronauts to Earth's Moon 49 years ago. Beyond Intrepid Crater and past long patches of rusty Martian desert lie peaks from the rim of large Endeavour Crater, visible on the horizon. The Opportunity rover continues to explore Mars, recently surpassing 5,000 Martian days on the red planet. via NASA

You may have heard of the Seven Sisters in the sky, but have you heard about the Seven Strong Men on the ground? Located just west of the Ural Mountains, the unusual Manpupuner rock formations are one of the Seven Wonders of Russia. How these ancient 40-meter high pillars formed is yet unknown. The persistent photographer of this featured image battled rough terrain and uncooperative weather to capture these rugged stone towers in winter at night, being finally successful in February of 2014. Utilizing the camera's time delay feature, the photographer holds a flashlight in the foreground near one of the snow-covered pillars. High above, millions of stars shine down, while the band of our Milky Way Galaxy crosses diagonally down from the upper left. via NASA

I love you so much that I brought you the Moon. Please take it before this tree becomes more interested. Also the Moon is heavier than I thought. And I foolishly picked it up by the hot side by mistake. But it is for you and, well, the others reading this APOD. Promise to keep this image -- our image -- in a safe place, and know that it was taken in a single, well-planned exposure in Valladolid, Spain. Please take it and keep it always as a token of our love and, well, April Fool's Day. via NASA